Modern computer operating systems often provide a desktop graphical user interface (“GUI”) for displaying various graphical objects. Some examples of graphical objects include windows, taskbars, docks, menus and various icons for representing documents, folders and applications. A user can interact with the desktop using a mouse, trackball, track pad or other known pointing device. If the GUI is touch sensitive, then a stylus or one or more fingers can be used to interact with the desktop.
Some computer applications include knobs, sliders and other controls that can be manipulated by a user through a pointing device or by touch input. For example, graphical objects emulating knobs and sliders of an audio mixing board or other hardware device can be included in the GUI of an audio or video application. The user can use a mouse or finger to rotate the knob control or move the slider control as desired to control a parameter of the application.
Many GUIs use knob controls to dial inputs up or down. However, traditional GUI knob controls typically have several drawbacks. For example, the interaction model of the knob control can be unclear, such that the user may not know whether to move a mouse pointer vertically, horizontally or in a circle to change the value of the knob control. Additionally, the resolution of a knob control may be less than other types of GUI controls (e.g., a slider control).